The present invention relates to a module for a modular conveyor belt with a roller conveyor surface and to a modular conveyor belt formed by a plurality of such modules.
Conveyor belts are known in the conveyor belts field, which are formed by a plurality of modules hinged to one another and the conveyor surface of which is defined by a plurality of rollers mounted on the modules themselves.
In particular, modules are known consisting of a base body that, at a front end and at a rear end with respect to the feeding direction of the belt is provided with one or more eyes, which receive pins for articulating with adjacent modules.
One or more coupling spaces are obtained in the base body for coupling with the gear teeth for driving the belt; as known, said spaces are accessible from the lower surface of the base body, namely from the surface opposite the one equipped with rollers.
From the upper surface of the base body supports protrude for supporting one or more shafts, on each of which a plurality of rollers adjacent to one another is mounted in a rotatable manner so as to form a row that extends substantially by the entire width of the module, except for the thickness of the supports. The conveyor surface of the belt is defined by the plane tangent to the outer lateral surface of the rollers. The upper surface of the modules is generally flat and between it and the lower directrix of the rollers a clearance exists such as to avoid, in use, jamming of the rollers following bending of the respective shaft due to the load acting thereonto.
Modules of the above-mentioned type are described, for example, in WO2014/066607-A1, AU-B-64692/86-B2 or NL1010530-C2 patent.
Modules of this type have the advantage of offering an almost continuous conveyor surface formed by the succession of rows of rollers. However, such modules have the drawback of having high sizes, in particular the height and weight, which penalise the conditions of use of the belts formed with them.
In particular, modules of this type have a high total height given by the sum of the thickness of the base body, the diameter of the rollers and the clearance existing between the rollers and the upper surface of the module itself. As known to the skilled person, this total height is directly correlated to the so-called “chordal effect” of opening and separating modules at the winding of the belt around the driving gear. Such a “chordal effect” is undesired since it causes problems of continuity of the conveyor surface at the fittings with the so-called “passage idle plates” arranged at the ends of the belt, as well as problems of safety of use, since, for example, the possibility exists that the operators may accidentally injure themselves.
Moreover, the total weight of these modules penalises the conditions of use of the belt, limiting, on the one hand, the load capacity and, on the other hand, encumbering the tensile stress status needed to be applied to the belt in order to draw it in motion.
Therefore the need has been felt for a long time to provide modules for modular conveyor belts with a roller conveyor surface which have overall a reduced total height and a lower weight compared with known modules, but substantially equal or slightly reduced mechanical strength characteristics.
In this respect, it has to be noted that, as known to the skilled person, in order to reduce the total height of the known modules, it is not possible to reduce at will the diameter of the rollers. On the one hand, in fact, the shaft on which the rollers are mounted must have a diameter such as to limit possible bending under load and that, therefore, must be greater than a defined lower limit. Moreover, on the other hand, in order to guarantee that a rotatable coupling is maintained between rollers and respective supporting shaft also under load, the ratio between the diameter of the shaft and that of the rollers must not be less than a defined lower limit.
In order to reduce the formation of separation openings between successive modules (i.e. the “chordal effect”) and, therefore, to limit the risk of crushing of operators intervening manually on the conveyor, US2013/0319824-A1 patent proposes to form at both opposite ends of each module of deflector elements that protrude from the upper surface of the module itself. According to what US2013/0319824-A1 patent describes, these deflector elements are hook shaped with a convex upper surface and extend above the cylindrical eyes for articulating with successive modules, without, however, protruding beyond the conveyor surface defined by the rollers. The deflector elements of successive modules interlock with one another so as to reduce the openings that separate the rollers of those modules, in particular at the sections in which the module articulates around the driving gear.
In order to reduce the total height and the weight of the roller modules of the known type and as described above, modules have been proposed, in the thickness of which the rollers have been incorporated. In these known modules the rollers are mounted coaxially to the pin that articulates successive modules; in practice, the rollers are housed in seats obtained in certain articulation eyes. The rollers of each module are, therefore, spaced by portions of module at which the spaces for coupling with the driving gear teeth are obtained.
Even these known modules have, however, some drawbacks. A first drawback is represented by the fact that the rollers are inevitably spaced from one another, so that it is impossible to obtain an almost continuous conveyor surface. The spacing of the rollers is due, on the one hand, to the impossibility of arranging the rollers at the portions of module in which the spaces for coupling with the driving gear teeth are obtained and, on the other hand, by the need of not excessively reducing the mechanical strength of the modules themselves.
A further drawback, in fact, is represented by the fact that these modules have poorer mechanical characteristics with respect to corresponding modules without rollers or with rollers supported above respective base bodies, the resistant section thereof being reduced by the containment seats of the rollers themselves.
WO2013/030404-A1 describes a module of a chain or of a roller belt wherein the rollers are incorporated in the body of the module itself in such a way that a lower portion of the rollers intersects the plane tangent to the upper surface of the hinge pins; therefore the rollers partially overlap the hinge pins along a direction orthogonal to the conveyor surface.
For this purpose, WO2013/030404-A1 teaches to form the module with a number of articulation eyes reduced and distributed differently with respect to the known modules. In particular, still according to WO2013/030404-A1, between articulation eyes that are successive and protruding from a same end of each module an empty space remains defined, which defines an area for housing at least one respective roller and at which the hinge pin that articulates the module to a successive module remains uncovered. Therefore, considering two successive modules articulated to one another, the respective rollers directly face the portion of the hinge pins adjacent to them, namely the outer lateral surface of the rollers directly faces the outer lateral surface of the portion of the hinge pins that extends at the respective housing area. According to WO2013/030404-A1, this allows reducing the distance between the outer lateral surfaces of the rollers and of the hinge pins to minimum values and, therefore, the overall height of the modules and the relative “chordal effect”.
However, such a configuration of the modules involves a reduction in the mechanical strength of the modular chain or belt under shear stress.